This invention relates to speech synthesis of freely generated text and, more particularly, to synthesis of freely generated text created by sound-impaired (hearing-impaired or speech-impaired) persons.
Dual Party Relay Service is a service that allows sound-impaired individuals to communicate with individuals who are not so impaired. By dialing a specified number, such individuals are interconnected to an attendant that connects the calling party to the called party and relays the established conversation.
More specifically, incoming calls from sound-impaired users are placed through a digital device, such as a Telecommunications Device for the Deaf (TDD) or a computer terminal and a modem. The sound-impaired user enters text through the TDD (or the like) and the text is received and displayed to the attendant. Through a separate connection, the attendant speaks the displayed text words to the unimpaired party, listens to the spoken response of the unimpaired party and transmits a written text message to the sound-impaired party which corresponds to the spoken response heard by the attendant. The sound-impaired party receives the written text message on a display device.
The above-described procedure suffers from lack of privacy. It is also very slow, cumbersome, and highly labor intensive. It would be highly beneficial to both the users and the telephone company to eliminate or at least reduce the attendant's involvement in calls to and from sound-impaired parties.
The potential clearly exists for eliminating the need for an attendant's assistance at least in the direction where text is converted to speech. One example is the "telephone information" service of AT&T and the Bell Operating Companies. In response to an inquiry, the telephone information operator accesses a data base, identifies the desired number and activates a synthesizer. However, this and all of the known other text-to-speech synthesizers systems deal exclusively with "canned" speech, which is speech (or text) with a predefined syntax and vocabulary.
In principle, it should be possible to enter the text generated by a TDD user into a speech synthesizer and have the synthesizer generate the spoken words which could be transmitted to a person who is not sound-impaired. In practice, this is not easy to do. Speech synthesizers convert text to speech exactly as the text appears. This requires the text to be correct, error free, properly punctuated and in standard syntax. Written language of the deaf, however, exhibits many departures from expected patterns of English syntax (or other languages, for that matter). The following three sentences are examples of written language of the deaf (WLD) texts that were produced by different writers:
They tend refusing to communicate. PA1 Some people have strong based on knowledges. PA1 I have many appointment from my childrens.
In a study of WLD, V. R. Charrow in Deaf English Technical Report 236, Institute for Mathematical Studies in the Social Sciences, Stanford University, 1974, asserts that the variability of WLD is systematic and rule-governed. She writes:
I suggest that the deaf are constructing a different variety of English, based on an internalization of certain rules of English, but not others, and affected, in some cases, by interference from ASL, whose rules are radically different from those of English. The result is the hypothesized `Deaf English`.
An examination of WLD syntax supports Charrow's claim. Although syntactic variation in WL texts appears random, a closer look shows that the variation is consistent. WLD exhibits a collection of non-standard features that can be identified and described. Some anecdotal evidence for this conclusion comes from the fact that standard English speakers usually adapt to the style after reading a number of WLD texts; serious comprehension problems seem to arise only when sentences are extremely telegraphic, word order is exceptionally free, or lexical choices are obscure.
In short, what is needed for the Dual Party Relay Service is the ability to accept and synthesize freely generated text; and the consistency of WLD suggests that computational analysis of this language style might be a feasible goal.